Targeting tumor microenvironment to curb chemoresistance via novel drug delivery strategies

Introduction: Tumor is a heterogeneous mass of malignant cells co-existing with non-malignant cells. This co-existence evolves from the initial developmental stages of the tumor and is one of the hallmarks of cancer providing a protumorigenic niche known as tumor microenvironment (TME). Proliferation, invasiveness, metastatic potential and maintenance of stemness through cross-talk between tumors and its stroma forms the basis of TME.

Areas covered: The article highlights the developmental phases of a tumor from dysplasia to the formation of clinically detectable tumors. The authors discuss the mechanistic stages involved in the formation of TME and its contribution in tumor outgrowth and chemoresistance. The authors have reviewed various approaches for targeting TME and its hallmarks along with their advantages and pitfalls. The authors also highlight cancer stem cells (CSCs) that are resistant to chemotherapeutics and thus a primary reason for tumor recurrence thereby, posing a challenge for the oncologists.

Expert opinion: Recent understanding of the cellular and molecular mechanisms involved in acquired chemoresistance has enabled scientists to target the tumor niche and TME and modulate and/or disrupt this communication leading to the transformation from a tumor-supportive niche environment to a tumor-non-supporting environment and give synergistic results towards an effective management of cancer.     

Correlation of Skp2 overexpression to prognosis of patients with nasopharyngeal carcinoma from South China

S-phase kinase-associated protein 2 (Skp2), which plays a role in cell cycle regulation, is commonly overexpressed in a variety of human cancers and associated with poor prognosis. However, its role in nasopharyngeal carcinoma (NPC) is not well understood. In this study, we examined the clinical significance of Skp2, with a particular emphasis on overall survival (OS) and disease-free survival (DFS), in NPC cases in South China, where NPC is an epidemic. Additionally, we explored the function of Skp2 in mai...     

Heterogeneity of hepatocellular carcinoma contributes to cancer progression

Hepatocellular carcinoma (HCC) is a highly heterogeneous disease displaying differences in angiogenesis, extracellular matrix proteins, the immune microenvironment and tumor cell populations. Additionally, genetic variations and epigenetic changes of HCC cells could lead to aberrant signaling pathways, induce cancer stem cells and enhance tumor progression. Thus, the heterogeneity in HCC contributes to disease progression and a better understanding of its heterogeneity will greatly aid in the development of strategies for the HCC treatment.     

Targeting CSCs within the tumor microenvironment for cancer therapy: a potential role of mesenchymal stem cells

Introduction: Mesenchymal stem cells (MSCs) are one subgroup of adult stem cells and possess a proliferative potential and ability to differentiate into various ceells.

Areas covered: Emerging evidence suggests that MSCs can reprogram toward cancer stem cells (CSCs), due to alterations of intrinsic and extrinsic microenvironments, leading to tumorigenesis. The CSC concept has fundamental clinical implications because of its involvement in cell migration/invasion, metastasis, and treatment resistance. Therefore, targeting CSCs provides a novel therapeutic strategy for cancer treatment. However, the origin of CSCs and its molecular connections are not fully understood. Emerging evidence suggests the existence of an inter-relationship between CSCs and epithelial-to-mesenchymal transition (EMT) phenotypic cells, in the context of inflammation and hypoxia, as well as the potential role of miRNAs.

Expert opinion: We suggest that targeting CSC signatures along with EMT, inflammation, and hypoxia will provide a more effective therapeutic approach for the elimination of CSCs. To that end, curcumin especially its synthetic novel analog CDF have been shown to attenuate CSC characteristics along with the deregulation of multiple pathways and miRNAs, leading to the inhibition of human tumor growth in vivo, suggesting the potential role of CDF as an anti-tumor agent for the prevention/treatment of tumor progression.     

Aberrant Expression of Markers of Cancer Stem Cells in Gastric Adenocarcinoma and their Relationship to Vasculogenic Mimicry

Background: Gastric cancer is the second leading cause of cancer-related death in Asia, and the majoritytype is gastric adenocarcinoma (GAC). Most GAC patients die of recurrence and metastasis. Cancer stem cells(CSCs) have been thought to be responsible for the initiation, development, metastasis, and ultimately recurrenceof cancer. In this study, we aimed to investigate expression and clinical significance of CSCs markers, CD133 andLgr5, and vasculogenic mimicry (VM) in primary GAC. Materials and Methods: Specimens from 261 Chinesepatients with follow-up were analyzed for CD133, Lgr5 protein expression and VM by immunohistochemicaland histochemical staining. The Pearson Chi’s square test was used to assess the associations among the positivestaining of these markers and clinicopathological characteristics. Postoperative overall survival time was werestudied by univariate and multivariate analyses. Results: In GAC tissues, positive rates of 49.0%, 38.7%, and26.8% were obtained for CD133, Lgr5, and VM, respectively. The mean score of microvessel density (MVD)was 21.7±11.1 in GAC tissues. There was a significantly difference between the positive and negative groups.There was a positive relationship between the VM, the expression of CD133 and Lgr5, and the score of MVDand the grades of tumor, lymph node metastasis, TNM stages (all p<0.05). The overall mean survival time ofthe patients with CD133, Lgr5, VM, and MVD (≥22) positive expression was lower than that of patients withnegative expression. The score of MVD, positive expression of CD133 and VM were independent prognosticfactors of GAC (p<0.05). Conclusions: VM, and expression of CD133, Lgr5, and the score of MVD are relatedto grades of tumor, lymph node metastasis, TNM stages, and overall mean survival time. It is suggested thatCSCs and VM could play an important role in the evolution of GAC.     

Immunohistochemical staining of cancer stem cell markers in hepatocellular carcinoma

Background

Cancer stem cells (CSCs) are thought to be a critical subpopulation in tumor development, progression, metastasis and recurrence, and the identification of these cells is an initial step in understanding their role in oncogenesis and in seeking valuable markers for diagnosis or development of targeting therapeutics.

Aims

To identify CSCs in hepatocellular carcinoma (HCC) specimens and define their tissue specificity.

Methods

Immunohistochemical staining of CSC markers: CD44, CD90, CD133 and aldehyde dehydrogenase (ALDH) was performed in 25 HCC specimens, 4 hepatoblastomas, 8 peri-malignant tissues, and 19 cases of viral hepatitis.

Results

The positivity of CD44 staining in HCC specimens was significantly lower than in viral hepatitis specimens. The positive rate of CD133 in HCC was similar to viral hepatitis specimens. CD133⁺ cells were largely localized to ALDH-positive cells in HCC as revealed by confocal microscopy. In contrast, the co-expression of both markers was visualized within vessels or in the portal areas in viral hepatitis. Moreover, among 7 liver specimens adjacent to HCC tissue, 3-6 samples were positive for CD44, CD90, CD133 and ALDH, especially in dysplastic cells. One of 4 hepatoblastoma cases was positive for all these markers; whereas, the other three specimens were negative for all these CSC markers.

Conclusions

In HCC and dysplastic tissues, clusters of CD133⁺/ALDH^high cells were identified. The use of cancer stem cell markers to screen tissues with chronic liver diseases provides limited guidance in the identification of malignant cells.